A new insight to adsorption and accumulation of high lead concentration by exopolymer and whole cells of lead-resistant bacterium Acinetobacter junii L. Pb1 isolated from coal mine dump

Abstract

A lead-resistant bacterial strain was isolated from coal mine dump and identified as Acinetobacter junii Pb1 on basis of 16S rRNA (ribosomal ribonucleic acid) gene sequencing. The minimum inhibitory concentration of lead for the strain was 16,000 mg l and it showed antibiotic and multi metal resistance. In aqueous culture, at an initial lead (Pb(II)) concentration of 100 and 500 mg l, lead adsorption and accumulation by the isolate was 100 and 60%, at pH 7 at 30 °C after 48 and 120 h, respectively. The two fractions of exopolysaccharide (EPS), loosely associated EPS (laEPS) and bound EPS (bEPS), and whole cells (devoid of EPS) showed high binding affinity towards Pb(II). The binding affinity of laEPS towards Pb(II) (1071 mg Pb g) was three times higher than that of bEPS (321.5 mg Pb g) and 6.5 times higher than that of whole cells (165 mg Pb g). The binding affinity of EPS and whole cells with Pb(II), reported in the current study, is considerably higher as compared to that reported in the literature, till date. SEM analysis, showed an increase in thickness of cells on exposure to Pb(II) and TEM analysis, revealed its accumulation (interior of cell) and its adsorption (with the external cell surface). The isolate was also found to be positive for indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production which helps in promoting plant growth. Thus, this study provides a new understanding towards Pb(II) uptake by A. junii Pb1, highlighting its potential on the restoration of Pb(II) contaminated repositories.

Evaluation of the cytotoxicity and interaction of lead with lead resistant bacterium Acinetobacter junii Pb1

“…Many researchers reported the increase in bacterial cell size in the presence of heavy metals using scanning electron microscopy (SEM). Increase in size of the bacterium on Pb(II) exposure has also been evidenced by SEM imaging [12]. Khan et al (2016) also used SEM to assess the impact of Cd(II) on the cell size of Salmonella enterica 43C and reported the increase in cell size in the presence of Cd(II) [21].…”

“…Microbial remediation of Pb(II) polluted sites has been considered as a cost effective, promising, and environmentfriendly approach as these microbes such as Acinetobacter junii Pb1, Pseudomonas stutzeri M-9, Vibrio harveyi M-11, and Ralstonia metallidurans CH34 are known to be resistant to heavy metals to a very high concentration [12][13][14]. Various mechanisms are known in microbes which help them to oppose the toxic effect of Pb(II).…”

“…Flow cytometer is a technology to characterize cell populations based on the measurement of scattered light and fluorescence emitted by dyes. Acinetobacter species shows different mechanisms for remediating the toxicity of lead via binding of lead on cell wall, adsorption on polysaccharides, extracellular sequestration, and efflux mechanism or by intracellular accumulation [12,13,16]. This helps in neutralizing the toxic effect of lead in the environment.…”

Lead soaps formation and biodiversity in a XVIII Century wax seal coloured with minium

“…The lead present in the seal can be also treated by detected Proteobacteria. In fact, adsorption and accumulation of Pb are properties displayed by Acinetobacter (Kushwaha et al ., ), while Bradyrhizobium and Methylobacterium were frequently isolated from lead contaminated soil (Khan et al ., ). Naik and Dubey () reviewed the different mechanisms employed by bacteria to resist high levels of lead and evidenced that extracellular sequestration, biosorption, precipitation and intracellular lead bioaccumulation are common in many groups of prokaryotes.…”

Valorization of coal fired-fly ash for potential heavy metal removal from the single and multi-contaminated system

“…has nowadays enhanced prominently, thus, diminishing the water eminence to the alarming levels (Wang et al., 2019a,b; Goswami et al., 2017a,b; Manikandan et al., 2016; Visa, 2016). Heavy metals are toxic and non-biodegradable pollutants which impose high toxicity even at a very low concentration and get accumulated in the food chain and adsorbed by the organisms resulting in severe health issues (Nebeská et al., 2018; Sathe et al., 2018; Kushwaha et al., 2019, 2017; Min et al., 2008).…”